The glycemic index is a value that measures the variation of blood glucose (blood sugar) concentration by showing how fast and to what level the blood glucose concentration increases during intake of particular food. The glycemic index demonstrates the rate with which a certain food converts into glucose and infiltrates the blood.
The glycemic index of a particular food product is a relative notion. It is based on the index of pure glucose, which is assumed to be 100. The glycemic index of other food products ranges from 0 to 100 depending on the rate of its absorption by human body. Food products with a high glycemic index induce a rapid increase of blood glucose concentration. They are easily digested and absorbed by human body. Food products with a lower glycemic index cause a tempered increase of blood glucose concentration, because carbohydrates that they contain are digested more slowly.
The glycemic index is defined as a ratio of the area under the so-called glycemic response curve, which shows the variation of blood glucose concentration from the time a meal was taken until the moment it gets completely assimilated by human body, to the area under a similar glycemic curve that reflects the intake of pure glucose equal in amount to the amount of carbohydrates contained in a given food product.
The glycemic index usually refers to a certain food product. A series of tests are conducted to record the glycemic curve observed when a test subject consumes a food product with a known amount of glucose. In other experiments, the same test subject consumes an equal amount of pure glucose. As a result, average values of said ratios are obtained for the areas under glycemic curves. The glycemic index is usually expressed as a percentage.
For practical purposes, tables of glycemic indices are compiled for various food products. An exemplary table is shown in: Kaye Foster-Powell, Susanna H A Holt, and Janette C Brand-Miller. International table of glycemic index and glycemic load values: 2002. Am J Clin Nutr.—2002, 76, 5-56.
However, such information on glycemic indices for particular food products can be insufficient for people, who, for example, follow a diet, in particular, monitor their glucose assimilation. Since the assimilation of food is individual for each person, they would like to know the glycemic index for specific food products they consume, rather than averaged data for separate products. In addition, they would like to know the glycemic index of the entire food they consume, consisting of a diverse set of food products, rather than the glycemic index of individual food products. And most important, an average consumer wants to know the glycemic index of food right after its assimilation instead of running experiments with food and pure glucose.
Initially, methods based on consumer's assessment of the effect of food-related carbohydrates using special tables based on experimental studies were widely used. Using the tables of glycemic indices of particular food products, a consumer can find a numerical value of the glycemic index, which characterizes the reaction of human body to carbohydrates incoming with meal. This calculation can be performed using remote databases that recognize the images of consumed food products transmitted from consumer's mobile devices. Such an approach provides only a rough evaluation of the glycemic index, because it refers to a specific food product, rather than to actually cooked food; besides the individual reaction of the body to this food is left out of consideration.
Application U.S. 2005/0266385 (published on Jan. 12, 2005, IPC A23L1/29) describes a method for monitoring the nutrition content information of consumables, and is intended to facilitate menu planning. The glycemic index of consumables is measured using the known glycemic indices for particular food products. This method does not provide for the evaluation of the glycemic index of food composed of different products.
Application WO 2008/009737 (published on 24 Jan. 2008, IPC A61B05/00) describes a method for glycemic index evaluation based on glycemic indices for particular food products, said indices being transmitted from a remote database to consumer's personal device. Based on the glycemic indices of individual food products, which compose consumer's meal, and their amount, the glycemic index of entire meal is calculated.
The method closest to the claimed invention measures the glycemic index of consumed food generating a feedback as described in international application WO 2002/005702 (published on Dec. 9, 2002, IPC A61B5/00). The core of the method is that the information on food to be taken at a meal, including its glycemic index and amount, is fed into computer beforehand. After the meal, blood glucose concentration is measured using one of the known methods. Based on the calculated values of blood glucose concentration, the glucose curve is modified and the glycemic index of the consumed food is adjusted in regard to a specific person. The resulting data are used to predict the blood glucose concentration and warn about its inadmissible increase, necessity to change eating behavior or undergo treatment.
The disadvantages of this method include the need to run multiple experiments in order to evaluate the glycemic index for each food product, which is inconvenient, since it requires multiple calculations and repetitive consumption of a certain product under the same conditions. This method cannot guarantee a stable, reproducible evaluation of the glycemic index for the same food product.
So, the need for a sufficiently fast and simple method of evaluating the glycemic index for a variety of food products, including meals of complex composition, is still actual. Additionally, this method needs to take into account the individual food assimilation features of a particular person and must provide sufficient accuracy.